September 3, 2008

Arctic Ice Shelf Breaks Away in Canada

Scientists said on Tuesday the ice shelves in Canada's High Arctic have lost a colossal area measuring 19 square miles after it broke away last month.

The remaining shelves attached to Ellesmere Island, which have lasted for thousands of years, have seen almost a quarter of their cover break away.

The Markham Ice Shelf, one of just five remaining ice shelves in the Canadian Arctic, split away from Ellesmere Island in early August. Scientists also reported that two large chunks totaling 47 square miles had broken off the nearby Serson Ice Shelf, reducing it in size by 60 percent.

"These substantial calving events underscore the rapidity of changes taking place in the Arctic," said Derek Mueller, an Arctic ice shelf specialist at Trent University in Ontario.

Experts say temperatures in large parts of the Arctic have risen far faster than the global average in recent decades, a development that is linked to global warming.

Mueller said the changes were irreversible under the present climate.

The total amount of ice lost from the shelves along Ellesmere Island this summer totaled 83 square miles -- more than three times the area of Manhattan Island, he said.

That is more than 10 times the amount of ice shelf cover that scientists estimated on July 30 would vanish from around the island this summer.

Dr. Luke Copland from the University of Ottawa said reduced sea-ice conditions and unusually high air temperatures have facilitated the ice shelf losses this summer.

"And extensive new cracks across remaining parts of the Ward Hunt Ice Shelf mean that it will continue to disintegrate in the coming years."

Scientists reported in July that substantial slabs of ice had calved from Ward Hunt Ice Shelf, the largest of the Ellesmere shelves.

Four other shelves have seen similar changes.

Once home to a single enormous ice shelf totaling around 3,500 square miles, Ellesmere Island now has four much smaller shelves that together cover little more than 300 square miles.

The ice shelves, which contain unique ecosystems that had yet to be studied, will not be replaced because they took so long to form, scientists said.

Loss of the extensive sea-ice in the Arctic has global implications. The "white parasol" at the top of the planet reflects energy from the Sun straight back out into space, helping to cool the Earth.

Continual loss of Arctic ice will see radiation absorbed by darker seawater and snow-free land, potentially warming the Earth's climate at an even faster rate than current observational data indicates.